The admixture zone of Betula humilis Schrk. phylogenetic lineages follows the eastern central European suture zone

Abstract

Background: Contemporary genetic variation across species ranges reflects Pleistocene climatic changes. The highest genetic diversity is usually found within areas of known or presumed glacial refugia and within the admixture zones of phylogenetic lineages.

Aims: The aim of our study was to evaluate the genetic diversity in the populations of Betula humilis, an endangered species, to distinguish between the refugial and suture zone hypotheses.

Methods: We used the PCR-RFLP method to analyse the chloroplast DNA variation in populations of B. humilis, distributed across north-eastern Poland, western Belarus and Latvia. Rarity index (DW) was calculated for each population based on ‘frequency-down-weighted marker values’. We tested phylogeographic structure by using the Permut software.

Results: The area studied was phylogeographically structured; DW values were low.

Conclusions: Based on the low DW values, we rejected the hypothesis of a periglacial refugium in north-eastern Poland and Belarus. Most likely, the substantial genetic diversity in the area under study is a consequence of the mixing of phylogenetic lineages derived from distinct glacial refugia. The admixture zone of B. humilis follows the eastern central European suture zone.

Keywords:

• Betula humilis
• chloroplast DNA
• conservation genetics
• PCR-RFLP method
• rarity index
• suture zone

Acknowledgements

We thank P. Jadwiszczak and L. Salmia for their help in the field. We are grateful to two anonymous reviewers for their constructive comments on the earlier draft of the manuscript.

The collection of material in Poland was approved by the Ministry of Environment (DOPpn-41020873/41255/11/RS, DLPpn-4102-90/8161/13/KW) and the Regional Director of Environmental Protection in Białystok (WPN.6402.15.27.2011.MW, WPN.6400.43.2012.WL). This work was supported by the Polish National Science Centre under grant no 2011/01/B/NZ8/01756.

Additional information

Notes on contributors

Katarzyna A. Jadwiszczak

Katarzyna A. Jadwiszczak is a population geneticist interested in the phylogeography and conservation genetics of endangered species.

Agata Banaszek

Agata Banaszek is an associate professor with research interests focused on the chromosome evolution, conservation genetics and phylogeography.

Agnieszka Chrzanowska

Agnieszka Chrzanowska is a M.Sc. student involved in the research of genetic diversity and differentiation of B. humilis populations.

Stanisław Kłosowski

Stanisław Kłosowski is a professor of biology focused on the phytosociology and ecology of wetland plants.

Oleg V. Sozinov

Oleg V. Sozinov is an associate professor. His research interests are in the composition and structure of natural phytocenoses, population biology and ecology of plants.